We've made this as painless as we could.
We learned a lot through our experiences with TFC, Counter-Strike, Day of Defeat, and so on. This engine is much more mod'able than Half-Life 1 was, and the tool set has been improved a lot. We'll also be releasing a bunch of material to help mod teams get their existing work up and running on the new engine.
The new Hammer will load Half-Life 1 levels (.RMF or .MAP source files only). You will need to retexture, and you'll probably need to redo most of the entities, but this is a major jumpstart compared to starting from scratch.
Models will need a little touching up in QC files and also need to be recompiled in order to work in the HL2 engine. Again, you must have the original source data in order to do this.Almost all parts of the HL2 SDK will be a little bit familiar to those who have worked with the HL1 SDK. Of course, there are a lot of new features, options, and systemic changes to explore, but overall the modding experience for HL2 is very similar to HL1. De FAQ bevat vooral veel antwoorden op technische vragen maar is toch interessant om te lezen voor de programmeer- en leveldesign-leek.